linux-kernel - Re: [PATCH 2/4] iio: light: stk3310: Implement vdd supply and power it off during suspend

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Date: Thu, 18 Apr 2024 11:06:32 -0400
From: Aren <aren@...cevolution.org>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Jonathan Cameron <jic23@...nel.org>, 
	Lars-Peter Clausen <lars@...afoo.de>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, Chen-Yu Tsai <wens@...e.org>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, Samuel Holland <samuel@...lland.org>, 
	Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>, Ondrej Jirman <megi@....cz>, 
	Uwe Kleine-König <u.kleine-koenig@...gutronix.de>, linux-iio@...r.kernel.org, phone-devel@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev, 
	Willow Barraco <contact@...lowbarraco.fr>
Subject: Re: [PATCH 2/4] iio: light: stk3310: Implement vdd supply and power
 it off during suspend

On Mon, Apr 15, 2024 at 05:04:53PM +0300, Andy Shevchenko wrote:
> On Sun, Apr 14, 2024 at 8:57 PM Aren Moynihan <aren@...cevolution.org> wrote:
> >
> > From: Ondrej Jirman <megi@....cz>
> >
> > VDD power input can be used to completely power off the chip during
> > system suspend. Do so if available.
> 
> ...
> 
> >  #include <linux/iio/events.h>
> >  #include <linux/iio/iio.h>
> >  #include <linux/iio/sysfs.h>
> 
> > +#include <linux/regulator/consumer.h>
> 
> Move it to be ordered and add a blank line to separate iio/*.h group.
> 
> ...
> 
> > +       data->vdd_reg = devm_regulator_get_optional(&client->dev, "vdd");
> > +       if (IS_ERR(data->vdd_reg)) {
> > +               ret = PTR_ERR(data->vdd_reg);
> > +               if (ret == -ENODEV)
> > +                       data->vdd_reg = NULL;
> 
> > +               else
> 
> Redundant 'else' when you follow the pattern "check for error condition first".
> 
> > +                       return dev_err_probe(&client->dev, ret,
> > +                                            "get regulator vdd failed\n");
> > +       }
> 
> ...
> 
> > +       if (data->vdd_reg) {
> > +               ret = regulator_enable(data->vdd_reg);
> > +               if (ret)
> > +                       return dev_err_probe(&client->dev, ret,
> > +                                            "regulator vdd enable failed\n");
> > +
> > +               usleep_range(1000, 2000);
> 
> fsleep()
> 
> > +       }
> 
> ...
> 
> >         stk3310_set_state(iio_priv(indio_dev), STK3310_STATE_STANDBY);
> > +       if (data->vdd_reg)
> > +               regulator_disable(data->vdd_reg);
> 
> I forgot to check the order of freeing resources, be sure you have no
> devm_*() releases happening before this call.

If I understand what you're saying, this should be fine. The driver just
uses devm to clean up acquired resources after remove is called. Or am I
missing something and resources could be freed before calling
stk3310_remove?

> ...
> 
> > +               usleep_range(1000, 2000);
> 
> fsleep()

Everything else makes sense, I'll include those in v2 along with a patch
to switch stk3310_init to dev_err_probe.

Thanks for taking the time to review
 - Aren